In Higher Plants by M E a N S of the Dna - Specific Probe 4 ' 6 - Diamidino - 2 - Phenylindole

The D N A in isola ted chloroplas ts was visual ized by the f luorescent p robe 4 '6 d i amid ino-2 -pheny l indo le ( D A P I ) . When exci ted with light of 360 nm, the D N A D A P I complex f luoresces bri l l iant ly at 450 rim. Nucle i also f luoresce but their nucleoli do not . RNase and Pronase t r ea tmen t of chloroplas ts did not affect the f luorescence but both preand pos t t r ea tmen t of D A P I s t a i n e d chloroplas ts with DNase specifically des t royed the f luorescence. D N A D A P I complexes in the chloroplas ts show up as br ight dots . These are d is t r ibuted uni formly within the ch loroplas t except for the ou te r margins. The f luorescent dots can be seen at different focal levels. The n u m b e r of D N A dots is roughly p ropor t iona l to ch loroplas t a rea which, in turn, is a function of leaf size. The n u m b e r of f luorescent dots also gave the impress ion that large leaves with large chloroplas ts conta in more chloroplas t D N A than nuclear D N A .